One example of base station antennas utilizing a wireless system such as a mobile telephone, a wireless LAN or WiMAX, particularly an MIMO (multi input multi output) system is a sector antenna which patch antennas for orthogonal polarized waves are arranged.
As the antenna for orthogonal polarized waves, the following constitution is proposed. Patent Document 1 describes a constitution of a two-frequency shared dipole antenna apparatus, and Patent Document 2 discloses a multi-frequency polarized wave shared antenna apparatus or a single frequency antenna apparatus.
Patent Document 1: JP-A 2006-325255 (Japanese Patent Application Laid-Open No. 2006-325255)
Patent Document 2: JP-A 2005-33261 (Japanese Patent Application Laid-Open No. 2005-33261)